| Abstract Scope |
Multiple advanced nuclear reactor concepts are utilizing graphite as a neutron moderator, reflector, and core configuration control, and semi-graphitic “matrix graphite” is used for TRISO fuel encapsulation to create pebbles and compacts. Graphite is not a fully dense material, meaning that it has regions of theoretical density carbon, but the remaining 15-25% is composed of porosity. The porosity is comprised of two different types of pores, closed porosity that isn’t available to gas permeation, and open porosity that allows for gas intrusion into the pores. The amount of closed and open pores, the size of the open pores, and their interconnectivity are strongly dependent on graphite grade. The nature of these pores can determine if the graphite grade is ideal for different reactor concepts. Gas-cooled reactors do not have significant concerns about coolant intrusion, whereas salt-cooled reactors do not want large pores or a pore network with interconnective pores that will allow for salt intrusion. Irradiation can cause changes to the pore network, and limited studies are available that quantify these changes. Work is on-going at ORNL to quantify the pore features in different graphite grades to support intrusion modeling efforts at NCSU. This presentation will discuss the on-going efforts at ORNL to quantify the pore networks and result from different graphite grades. |